typical HFE's of 2N3440 and 2N5416

[Wagener]

I bought a few transistors from a (cheap) place and I measured the hfe's with my multimeter.

Some of them has a hfe of 60, others 90 and some 0.


Please comment on this.

I suppose the ones with hfe 0 is useless? It is for my amplifier project.

[Wagener]

I cleaned the leads and now I read a hfe on every one.

All the 2N5416's have hfe of 100 except one which had hfe of 66.

2N3440's had hfe's of about 69-72 except one which had a hfe of 58.

Is this ok?

Is the hfe of these transistors high enough? I checked the datasheets and the specify hfe's of 40-160 for 2N3440 and 30-150 of 2N5415

Can I use transistors with different hfe's?

[Nelson Pass]

Those are typical numbers. I used to select for about 100
in early Threshold product.

[fab]

Originally posted by Wagener
Can I use transistors with different hfe's?

Try to match hfe for less than 15% difference between NPN and PNP for the same pair when used in a complementary circuit.

[slowhands]

Originally posted by Wagener
...All the 2N5416's have hfe of 100 except one which had hfe of 66. 2N3440's had hfe's of about 69-72 except one which had a hfe of 58. Is this ok?

Is the hfe of these transistors high enough? I checked the datasheets and the specify hfe's of 40-160 for 2N3440 and 30-150 of 2N5415. Can I use transistors with different hfe's?

These values are within the range of Hfe specified for these parts. Actually they are fairly well matched for a random handful of parts. For most applications they are just fine.

If you want to use these part types in a design, you should assume that you may ocasionally get parts with either higher or lower Hfe, still within spec. Ideally you should allow for that. In other words, for minimum cost, design your circuit so that parts with Hfe anywhere in the spec range will still work.

You can select for a narrower range of Hfe, but it adds cost in manufacturing and field support, something to weigh. If they are used in a differential amp, you may want to consider matching them, but that is about the only case I can think of.

These are typically used for VAS and pre-drivers, which typically do not require selected or matched parts. I assume that is your application, in which case they well vetted for the roles, since they have been used for decades in those positions, without selection or matching.